Modern diving snorkels include fluid flow systems which are intended to facilitate underwater breathing in two ways: by expelling water and exhaust gases from the snorkel; and by providing an unimpeded supply of fresh air to the diver. These objectives may be accomplished by utilizing a system of check valves on the snorkel in the manner shown in U.S. Pat. No. 4,655,2I2 to Delphia and U.S. Pat. No. 3,860,042 to Green. Such systems include an intake valve disposed near the top of the snorkel for allowing fresh air into the snorkel tube. Such systems also include an exhaust valve disposed along the snorkel tube between the snorkel mouthpiece and the air intake valve. The respective valves function so that when the diver inhales, the intake valve opens and the exhaust valve closes. In this manner only fresh air may enter the snorkel tube. When the diver exhales, the intake valve closes and the exhaust valve opens. The pressure from the diver's exhaling forces exhaust gases and any water which may have entered the snorkel tube out of the snorkel tube through the exhaust valve.
The intake valve in the prior art patents is generally a flexible diaphragm which has a center fixed to a valve seat located near the air intake opening of the snorkel tube. The outer portion of the diaphragm flexes into and out of engagement with the valve seat to close or open the air passageway in response to the diver's breathing. The center of the diaphragm remains in the same location throughout the cycle--fixed closely to the valve seat.
Unfortunately, since the entire diaphragm remains so close to the air intake opening when the diver inhales, the flow of air into the tube through the air intake opening is impeded, with the result that breathing is more difficult for the diver than if the diaphragm could move totally away from the air intake opening.
Also, because the air intakes face up (i.e away from the waterline) on the Delphia and Green snorkels when these snorkels are used in the above-water position, water splashing into the air intake can enter by force of gravity into the breathing tube, hampering the breathing of the diver.